Charles Cave b1750 Compton Dundon

Was a yoeman farmer at Stoke-sub-Hamden, Married Sarah Hill, had 11 children, one died as teen, emigrated 1848/9 to Australia. He had leases on many blocks of land therefore would have had bank records. Trying to find out which ship and to whom he paid for voyage by bank records??? No success through Nat Library, Aust., State Library, SAust,Somerset Heritage Centre, Passenger Lists etc. His brother-in-law took over the farm in 1847.
Does anyone have suggestions?